want to know precise GC benchmarks

[Rainer Schuetze]

On 01/10/2019 18:24, a11e99z wrote:
> On Tuesday, 1 October 2019 at 16:12:18 UTC, a11e99z wrote:
>> does anybody some kind of benchmark to test conservative and precise GC?
>> precise GC is better or not? is STW improving?

Without false pointers the precise GC is usually a bit slower (by a few
%) due to additional work being done during allocations. But it can be a
lot faster if there are false pointers that pin large amounts of memory
still needed to be scanned during collections. False pointers are more
likely for 32-bit processes, but can also happen with 64-bit processes
(also depending on addresses used by OS allocations: OSX worse than
Windows worse than Linux).

> 
> and another question about GC and app parameters:
>> program.exe “–DRT-gcopt=gc:precise parallel:4”
>> “–DRT-scanDataSeg=precise” <input.data >output.data
> are this 2 -DRT params combined or overwriting each other?
> link to doc for DRT+GC https://dlang.org/spec/garbage.html#gc_config

These options are independent and can be used in arbitrary order. The
last option wins if you actually overwrite an option, e.g.
'“–DRT-gcopt=gc:precise parallel:4” “–DRT-gcopt=parallel:7”' will still
use the precise GC, but 7 mark threads.

Please note that “–DRT-scanDataSeg=precise” is only supported on Windows.

> 
> I know about rt_options[] but asking about program args
> 
> why I want to know such info?
> CodinGame sometimes use time-limit for bot move for example 100ms, and
> bot will be disqualified in case no answer

There is no actual upper limit for the collection time, it mostly
depends on how much life memory has to be scanned.